update doc.

git-svn-id: svn+ssh://ci.ruby-lang.org/ruby/trunk@40064 b2dd03c8-39d4-4d8f-98ff-823fe69b080e

io.c

@@ -10684,30 +10684,19 @@ static VALUE argf_getpartial(int argc, VALUE *argv, VALUE argf, int nonblock);
  *     ARGF.readpartial(maxlen)              -> string
  *     ARGF.readpartial(maxlen, outbuf)      -> outbuf
  *
- *  Reads at most _maxlen_ bytes from the ARGF stream. It blocks only if
- *  +ARGF+ has no data immediately available. If the optional _outbuf_
- *  argument is present, it must reference a String, which will receive the
- *  data.
+ *  Reads at most _maxlen_ bytes from the ARGF stream.
+ *
+ *  If the optional _outbuf_ argument is present,
+ *  it must reference a String, which will receive the data.
  *  The <i>outbuf</i> will contain only the received data after the method call
  *  even if it is not empty at the beginning.
- *  It raises <code>EOFError</code> on end of file.
  *
- *  +readpartial+ is designed for streams such as pipes, sockets, and ttys. It
- *  blocks only when no data is immediately available. This means that it
- *  blocks only when following all conditions hold:
+ *  It raises <code>EOFError</code> on end of ARGF stream.
+ *  Since ARGF stream is a concatenation of multiple files,
+ *  internally EOF is occur for each file.
+ *  ARGF.readpartial returns empty strings for EOFs except the last one and
+ *  raises <code>EOFError</code> for the last one.
  *
- *  * The byte buffer in the +IO+ object is empty.
- *  * The content of the stream is empty.
- *  * The stream has not reached EOF.
- *
- *  When +readpartial+ blocks, it waits for data or EOF. If some data is read,
- *  +readpartial+ returns with the data. If EOF is reached, readpartial raises
- *  an +EOFError+.
- *
- *  When +readpartial+ doesn't block, it returns or raises immediately.  If
- *  the byte buffer is not empty, it returns the data in the buffer. Otherwise, if
- *  the stream has some content, it returns the data in the stream. If the
- *  stream reaches EOF an +EOFError+ is raised.
  */
 
 static VALUE